Interactions between Viruses and Virus Strains

Abstract

Publisher Summary Plants infected with one virus usually retain susceptibility to infection by other unrelated viruses. Therefore, a plant may, and frequently does, carry more than one virus. Double, triple, or even quadruple infections are not uncommon under natural conditions. Peach trees carrying ring-spot virus may become infected with mosaic, yellows, or any one or more of a number of virus diseases to which stone fruits are susceptible. In the western United States, sugar beet plants are frequently found infected with curly top, virus yellows, and mosaic and, experimentally, sugar beet has been infected successively with the viruses of curly top, mosaic, yellow net, and dodder latent mosaic. Apparently none of these interferes measurably with any one of the others. Each virus increases, invades the plant according to its own peculiar pattern, and produces its own characteristic effects. However, a few viruses are known that interfere with the normal development or expression of other viruses unrelated to them. These interactions are expressed by partial or complete suppression of one virus by another, by synergistic associations, by modification of the type of symptoms that appear on the host plant, or by abnormal increase in the concentration of one virus. By far the most extensive interactions occur, however, between different strains of the same virus. These interactions, so far as discovered, are antagonistic in nature. This chapter starts with the discussion on the interactions among unrelated viruses. It also discusses the interactions between the virus strains.